Immunology: Repeat trials of oocyte donation to women with previous donor oocyte success

Oocyte donation has proven to be highly successful in establishingpregnancy in functionally agonadal women. Both implantationand ongoing pregnancy rates in women using this method havesurpassed those normally seen in standard in-vitro fertilization(IVF) patients. Over a 5 year period, seven women who had previouslyconceived using oocyte donation elected to attempt pregnancyand deliver a second child using the same donor. In each casethe paramount consideration was to provide a sibling of thesame genetic make-up as the child or children previously borne.Of the seven women studied, whose ages ranged from 24 to 44years, five became pregnant on subsequent cycles. The time toconception varied from one to a maximum of three attempts withthree of the five women becoming pregnant on the first cycleand two requiring three cycles to establish the subsequent pregnancy.The overall rate of success in this group was 12 pregnanciesin 20 cycles of embryo transfer (60%). An exaggerated implantationrate (25.6%) was also noted (23 individual embryo implantationsfrom 90 embryos transferred). Of the 12 pregnancies establishedin these seven women, four (33%) were multiple gestations (threetriplets, one twin). We conclude that women who have previouslyexperienced pregnancy following oocyte donation are highly likelyto conceive in a subsequent trial at a rate that may be higherthan that normally seen in the general population of women undergoingoocyte donation.     

Obstetric and perinatal outcome after oocyte donation: comparison with in-vitro fertilization pregnancies

The obstetric and perinatal outcome in 51 oocyte donation pregnancies (61 infants) was compared with that of a control group of standard in- vitro fertilization (IVF) patients (97 pregnancies, 126 infants). The oocyte recipients (mean +/- SD age 33.5+/-4.7 years) included 39 women with ovarian failure and 12 women with functioning ovaries. In oocyte recipients, first trimester bleeding (53%) occurred significantly more often than in IVF mothers (31%, P < 0.01). Pregnancy-induced hypertension was observed in 31% of oocyte recipients compared with 14% in IVF mothers (P < 0.05). There was no difference in the duration of pregnancies or in the preterm delivery rate between the two groups. When restricting analysis to singleton pregnancies, 63% of oocyte recipients were hospitalized in the antenatal period compared with 29% in the IVF group (P < 0.001). The Caesarean section rate was 57% in the oocyte donation group and 37% in the IVF group (P < 0.05). Birthweight in singleton pregnancies was similar in both groups. The perinatal mortality rate was 3.3% in the oocyte donation group and 0% in the IVF group. In conclusion, oocyte donation pregnancies are associated with an increased risk compared with IVF pregnancies, but the complications are usually manageable and most oocyte recipients experience a good pregnancy outcome.      

The optimal number of embryos to be transferred in shared oocyte donation: walking the thin line between low pregnancy rates and multiple pregnancies

There has been growing concern about the number of multiple gestations resulting from assisted reproductive technologies. For in-vitro fertilization (IVF), there are guidelines concerning the number of embryos to be transferred. In oocyte donation, however, there is a paucity of studies addressing this issue and common practice is extrapolated from standard IVF procedures. This may not be correct since endometrial receptivity has been shown to be altered in oocyte donation. Thus the purpose of this study was to assess the optimal number of embryos to be transferred in oocyte donation. The study population included 254 patients with ovarian failure who underwent a total of 601 embryo transfers in a single shared oocyte donation programme. Pregnancy rates (PRs), multiple pregnancies, triplet pregnancy rates, and implantation rates were evaluated according to the number of embryos transferred. A significant linear increase in PRs was noted with the increasing number of embryos transferred up to five (11.1% for one embryo, 36.7% for five embryos). Multiple pregnancies increased significantly from 15.8% for two embryos transferred, to 44.4% for five embryos. The rate of triplet pregnancies also increased from 2.7% for three embryos transferred, to 8.3% for five embryos. Optimization of the number of embryos to be transferred is discussed.      

Serum pregnancy-specific beta1-glycoprotein before embryo transfer is related to endometrial thickness and to outcome prognosis in women undergoing in-vitro fertilization treatment

We have previously observed the repeated presence of low but detectable amounts of the trophoblast marker pregnancy-specific beta1-glycoprotein (SP1) in the serum of some women undergoing in-vitro fertilization (IVF) treatment around the time of oocyte retrieval. The occurrence of these signals seemed to be restricted to a defined group of patients which also showed a lower pregnancy success rate in a preliminary study. To test our hypothesis we have analysed 173 consecutive cycles leading to an embryo transfer. Fifty-four cycles (31%) had a serum SP1 level of at least 0.1 ng/ml between days embryo transfer -5 and embryo transfer (group A). Five pregnancies were obtained in this group (pregnancy rate = 9.3%), while in group B, defined by the absence of detectable SP1 before embryo transfer (119 cycles), 36 ongoing pregnancies were achieved (30.3%). Ten of the 41 pregnancies were achieved in 33 first-time non-pregnant patients undergoing further attempts during the study period. Again the pregnancy rate was higher in the first-time group B women (9/23 versus 1/10 for group A). Patients tended to remain in their groups A or B, the latter being associated with a better immediate as well as subsequent chance for pregnancy. Group A cycles had a significantly lower endometrial thickness two days before oocyte retrieval than group B (P = 0.0011). We postulate that the presence of an unknown, maternal and progesterone- or follicle stimulating hormone-independent factor in some patients could stimulate tonic ectopic SP1 synthesis and at the same time negatively influence endometrial development.      

Oocyte donation in patients with Turner's syndrome: a successful technique but with an accompanying high risk of hypertensive disorders during pregnancy

BACKGROUND: Few data are available on pregnancy rate and obstetrical outcome after oocyte donation in Turner's syndrome patients. We conducted a retrospective analysis on the outcome of this subgroup. METHODS: Thirty oocyte donation cycles with fresh embryo transfer were performed in 21 patients between 2001 and 2004. RESULTS: The mean (+/-SD) age of the recipients was 33.1+/-1.8 years. The median (range) number of transferred embryos per cycle was two (1-4). Seventeen pregnancies were obtained (57%), of which 12 were clinical (40%). The implantation rate and the ongoing pregnancy rate were 22% (15 out of 68) and 30% (nine out of 30), respectively. Premature delivery was observed in 50% (four out of eight) of the pregnancies and intrauterine growth retardation in 55.5% (five out of nine) of the fetuses. Hypertensive disorders occurred in five out of eight pregnancies (three pre-eclampsias). CONCLUSIONS: Turner's syndrome patients achieve acceptable pregnancy rates after oocyte donation. A high rate of pregnancy-associated hypertensive disorders was observed which have led to a high rate of prematurity and intrauterine growth restriction. Although the number of cases in this study is limited, these results call for the need for intensive surveillance of such pregnancies. In order to reduce the risk of hypertensive disorders induced by multiple pregnancies, single embryo transfer should be proposed.     

Conversion of cycles involving ovarian hyperstimulation with intra-uterine insemination to in-vitro fertilization

Conversion to in-vitro fertilization (IVF) and embryo transferas an alternative to cancellation was offered in 27 consecutivecycles of controlled ovarian hyperstimulation and intra-uterineinsemination (IUI) cycles with excessive follicular developmentin patients with idiopathic infertility. IVF and embryo transferwas performed in 25 cycles, resulting in 13 pregnancies (52%),with 22% of couples having at least two embryos cryopreserved.The pregnancies have resulted in one singleton and two twinbirths, one spontaneous abortion, and nine ongoing pregnancies(including one triplet gestation). Four patients developed severeovarian hyperstimulation syndrome (OHSS) after IVF and embryotransfer, including two cases requiring paracentesis. Threeof four OHSS patients were pregnant, resulting in live birthsof healthy twins, one spontaneous abortion and one ongoing singletongestation. In two cycles a spontaneous luteinizing hormone (LH)surge occured, preventing oocyte retrieval. For these two women,drainage of all follicles except the five most likely to fertilize(18–22 mm diameter) was performed, followed by IUI, withno pregnancies or OHSS observed. Conversion of patients fromIUI cycles to IVF/embryo transfer cycles avoids cancellationof the very cycles with the best chance of achieving pregnancy.OHSS remains a problem, necessitating extensive pre-IVF counsellingand post-transfer vigilance.     

In-vitro fertilization in infertile women with the polycystic ovarian syndrome

Forty-four infertile patients with the polycystic ovarian syndrome (PCOS) resistant to other treatment modalities were treated in 58 cycles of IVF after accomplishment of pituitary gonadotroph suppression with a GnRH-agonist. Four cycles were cancelled before oocyte retrieval while embryo transfer was deferred for 10 cycles due to imminent ovarian hyperstimulation syndrome (OHSS). Follicle aspiration yielded 18.8 +/- 9 oocytes per cycle. The cleavage rate was 68%. There was no cleavage in five cycles. The pregnancy rate was 33.3% per embryo transfer. In 32 cycles 9.0 +/- 5 suitable supernumerary embryos were cryopreserved. Transfer of cryopreserved embryos gave three additional pregnancies. The accumulated pregnancy rate per patient was 36%. In clomiphene citrate resistant patients, transfer of cryopreserved embryos was accomplished after secretory transformation of the endometrium by oestradiol/progesterone substitution. Although seven pregnancies ended in a miscarriage, the 'take-home' baby rate was 20%. OHSS ensued in 28 (46.7%) cycles. In PCOS, in-vitro fertilization following pituitary gonadotroph suppression seems a treatment alternative with pregnancy rates comparable to normo-ovulatory women with tubal factor infertility. However, the incidence of OHSS is high and constitutes the major problem of cycle control.     

冻融胚胎移植30周期分析

目的探讨冷冻胚胎复活情况及妊娠.方法对2001年9月～2003年9月在本中心实施体外授精胚胎移植失败,再次行冻融胚胎移植30周期28人进行回顾性分析.结果 30周期28人共冷冻胚胎150个,复活91个,复活率60.7%,妊娠8例,冷冻胚胎的妊娠率28.6%,周期妊娠率26.7%.结论冻融胚胎移植能增加一次取卵的总妊娠率,降低多胎率.     

Cumulative conception and live birth rates after oocyte donation: implications regarding endometrial receptivity

The purpose of the present study was to determine the cumulative likelihood of pregnancy success after repetitive cycles of oocyte donation and specifically to examine the influence of recipient age and diagnosis upon the cumulative likelihood of pregnancy in an effort to identify any potential subgroup of recipients who might have diminished endometrial receptivity. We retrospectively analysed the outcome of 418 consecutive embryo transfer cycles among 276 recipients of oocyte donation in our institution. We analysed clinical pregnancy and delivery rates in the recipients divided by age groups and diagnostic groups. For the purpose of life-table analysis, only cycles prior to and including the first cycle producing a successful pregnancy were included. Frozen-thawed embryo transfers were not included in the analysis. The overall clinical pregnancy rate was 36.2% (95% CI 31-41%) and the cumulative pregnancy rate after four cycles was 87.9%. The overall delivery rate was 29.3% (95% CI 25-33%) and the cumulative delivery rate after four cycles was 86.1%. There were no statistically significant differences in any of the rates attributable to recipient age or diagnosis. No decline in per cycle success was noted over consecutive cycles. We conclude that neither recipient age nor diagnosis plays a substantial role in the success of oocyte donation, implying that endometrial receptivity is unaltered by age or diagnosis. Furthermore, up to four successive cycles of oocyte donation are associated with the same probability of success.      

Turner's syndrome and pregnancies after oocyte donation

A total of 20 clinical pregnancies was achieved among 18 women with Turner's syndrome who were treated in an oocyte donation programme. The oocytes were donated by voluntary unpaid donors. A mean of 1.8 embryos per transfer was given to each recipient by way of 28 fresh and 25 frozen embryo transfers. With fresh and frozen embryos, 13 and seven pregnancies respectively were achieved. The clinical pregnancy rate per fresh embryo transfer was 46%, and the implantation rate 30%, being similar to the corresponding rates among our oocyte recipients with primary ovarian failure in general. The corresponding rates with frozen embryos were 28 and 19%. Of these pregnancies, 40% ended in miscarriage. This high rate may be explained by uterine factors. Six women were hypertensive during pregnancy, a rate comparable with that in other oocyte donation pregnancies. All these women delivered by Caesarean section. Pregnancy and implantation rates after oocyte donation were high in women with Turner's syndrome, but the risk of cardiovascular and other complications is high. Careful assessment before and during follow-up of pregnancy are important. Transfer of only one embryo at a time to avoid the additional complications caused by twin pregnancy is recommended.     

Infertility: Semi-programmed ovarian stimulation as the first choice in in-vitro fertilization programmes

The objective of this work was to evaluate the results obtainedwith a protocol of semi-programmed ovarian stimulation (low-dosecontraceptive pill + clomiphene citrate + human menopausal gonadotrophin+ dexamethasone) used as the first-choice method for in-vitrofertilization (IVF). A total of 207 punctures was performedfor oocyte collection from 168 patients (mean age 31.0 ±4.0 years); mean infertility duration was 5.81 ± 3.30years. The infertility factors indicating IVF for this populationwere as follows: tubo-peritoneal factor, 68%; pure or associatedmale factor, 9.2%; endometriosis, 11.1%; ovulatory factor, 4.3%;idiopathic factor, 11.6%; others, 2.4%. No oocyte was foundon aspiration in five procedures (2.4%), with the mean numberof oocytes collected per cycle being 5.87 ± 3.3 (range0–18). The cancellation rate per puncture was 5%. Themean embryo cleavage rate was 60.2 ± 36.8%, with transferof at least one embryo occurring in 82.6% of all punctures.The mean number of transferred embryos was 2.52 ± 1.60(range 1–5). The clinical pregnancy rates per startedcycle and per puncture were 22.4 (218 ovarian stimulation cycles)and 23.6% (a total of 49 clinical pregnancies, 36 single, ninetwins and four triplets) respectively. The clinical pregnancyrate per embryo transfer was 28.6%. The embryo implantationrate was 12.6%. The abortion rate was 16.3%. The index of deliveriesper puncture was 19.8%. There were no cases of moderate or severeovarian hyperstimulation syndrome. The favourable results obtained,in addition to the low operational costs, confirm the validityof the use of semi-programmed cycles as the first choice forpatients undergoing the IVF process.     

Elective single embryo transfer yields good delivery rates in oocyte donation

BACKGROUND: High pregnancy rates have been noted after oocyte donation (OD). Multiple pregnancies should be avoided, because oocyte recipients have an increased risk of obstetric complications. METHODS: We analysed our OD results from 2000-2001 when elective single embryo transfer (eSET) was introduced as a recommended policy for all recipients if at least one good quality embryo was available. The results were compared with those achieved in 1998-1999, when usually two embryos were transferred (double embryo transfer, DET). Between 1998 and 2001, 100 healthy women donated oocytes and 135 fresh embryo transfers were carried out. The mean age of the donors was 31 years and that of the recipient women was 35 years. RESULTS: The proportion of eSET of all OD transfers was 17.1% in 1998-1999 and 61.0% in 2000-2001. There was no statistically significant difference in clinical pregnancy (36.8 versus 45.8%) and delivery rates (31.6 versus 33.9%) per embryo transfer between the two time periods. The proportion of twins declined from 29% (1998-1999) to 10% (2000-2001). The delivery rate was similar after eSET and DET (32.6 versus 32.1% respectively). CONCLUSIONS: By increasing the proportion of eSETs it is possible to reduce the number of twins without affecting delivery rates in oocyte recipients.     

The "vanishing embryo" phenomenon in an oocyte donation programme

BACKGROUND: We studied the incidence of vanishing embryos (VE) in pregnancies achieved by oocyte donation and evaluated the obstetric and perinatal complications. METHOD: A retrospective study was carried out based on a chart review of 399 patients with multiple pregnancies from our oocyte donation programme. We defined vanishing phenomenon as the early resorption, in the first trimester, of one or more embryos in a multiple gestation, after confirming embryonic heart activity by transvaginal ultrasound. RESULTS: Vanishing embryo was observed in 75 patients (18.8%). In 60 patients (80%) this phenomenon occurred before the ninth gestational week. A higher incidence of VE was observed in patients who initially showed a higher number of gestational sacs (P < 0.03). Vaginal bleeding in the first trimester was significantly higher in patients with VE (P < 0.005). Miscarriage rate was similar in pregnancies with and without VE (P = NS). The incidence of pregnancy induced hypertension was decreased in the group with VE (P < 0.03). Preterm spontaneous rupture of membranes occurred more frequently in pregnancies with VE (P < 0.05). However, gestational age at delivery was similar in the group with VE and the controls. CONCLUSIONS: The high incidence of VE in pregnancies achieved by oocyte donation should be considered when counselling patients with high order multiple gestations.     

Human zona pellucida micromanipulation and monozygotic twinning frequency after IVF

To assess the association of zona pellucida micromanipulation and subsequent development of monozygotic twins, cases of assisted embryo hatching (AH) and intracytoplasmic sperm injection (ICSI) were identified and related to treatment type, implantation and zygosity data. Embryology records from all patients undergoing in-vitro fertilization (IVF) at this centre from January 1995 to March 1998 were reviewed. In this study, 3546 transfer cycles were completed, with clinical pregnancy established in 1911 (54% per transfer) patients undergoing a single IVF cycle. These pregnancies occurred in 1674 (88%) IVF cycles, 120 (6%) donor oocyte cycles (DER), and 117 (6%) frozen embryo transfer (FET) cycles. During the study period, 23 cases of monozygotic (MZ) twins were identified, representing an overall frequency of 1.2%. Chorionicity was determined by transvaginal ultrasound at 7 weeks when the number of embryos transferred was less than the number of fetal heart-beats, or when >1 fetal heartbeat per gestational sac was seen. Zygosity was confirmed by placental evaluation at delivery, and corroborated the antenatal diagnosis in all cases. Among IVF study patients the frequency of MZ twinning was not statistically different between zona manipulated and zona intact subgroups. While this investigation is the largest to date describing the relationship between MZ twins and zona procedures, studies with even greater statistical power are needed to clarify it more precisely, particularly in DER and FET settings. A greater overall frequency of MZ twinning for IVF patients may be a function of the higher number of embryos transferred in IVF, rather than discrete zona manipulations.     

Endocrinology: High incidence of embryo transfer cancellations in patients with polycystic ovarian syndrome

This study was aimed at assessing the outcome of in-vitro fertilization(IVF) and embryo transfer in patients with polycystic ovariansyndrome (PCOS). The results of IVF and embryo transfer in PCOSpatients (PCOS group, 78 cycles of 26 patients) were comparedwith those of a control group (423 cycles in 202 patients withoutmale factor; age and ovarian stimulation protocol were matched).Although the pregnancy rate per transfer was not different inthe two groups of patients (25 versus 34%, PCOS versus controlgroup), the PCOS group had a significantly lower pregnancy rateper follicle aspiration (19 versus 31%, P < 0.05). A notableresult was a significantly higher incidence of embryo transfercancellations in the PCOS group (22 versus 8%, P < 0.01),which resulted from unpredictable failure of either oocyte recoveryor fertilization. The incidence of unexplained complete failureof fertilization was significantly higher in the PCOS group(18 versus 5%, P < 0.01). These results may reflect a reducedquality of the oocytes in the PCOS group, and there was a subgroupof PCOS patients who repeatedly produced poor results of treatment.Although the ovarian stimulation regimen best suited to PCOSpatients remains to be determined, special care should be takenduring ovarian stimulation, especially when the PCOS patientshad experienced unexplained failure of oocyte recovery or fertilizationin the previous treatment cycle(s).     

Minimal stimulation IVF with late follicular phase administration of the GnRH antagonist cetrorelix and concomitant substitution with recombinant FSH: a pilot study

BACKGROUND: The use of the natural cycle for IVF offers the advantage of a patient-friendly and low-risk protocol. Its effectiveness is limited, but may be improved by using a GnRH antagonist to prevent untimely LH surges. METHODS: In this pilot study, minimal stimulation IVF with late follicular phase administration of the GnRH antagonist cetrorelix and simultaneous substitution with recombinant FSH was applied for a maximum of three cycles per patient. Main outcome measures were pregnancy rates per started cycle and cumulative pregnancy rates after three cycles. RESULTS: A total of 50 patients completed 119 cycles (2.4 per patient). Fifty-two embryo transfers resulted in 17 ongoing pregnancies [14.3% per started cycle; 32.7% per embryo transfer; 95% confidence interval (CI) 7.9-20.7% and 19.7-45.7%, respectively]. One dizygotic twin pregnancy occurred after transfer of two embryos, the other pregnancies were singletons. The cumulative ongoing pregnancy rate after three cycles was 34% (95% CI 20.6-47.4%). Live birth rate was 32% per patient (95% CI 18.8-45.2%). CONCLUSIONS: Pregnancy rates after IVF with minimal, late follicular phase stimulation are encouraging. Considering the low-risk and patient-friendly nature of this protocol, it may be a feasible alternative to IVF with ovarian hyperstimulation.     

71例自然周期IVF—ET技术临床应用分析

目的探讨自然周期方案体外受精-胚胎移植（IVF—ET）技术在卵巢低反应、卵巢肿瘤不孕患者中的应用。方法对珠海市妇幼保健院生殖中心2007年2月至2008年11月共71例不孕症患者采用自然周期方案进行IVF—ET的临床资料进行回顾性分析。结果71例中65例是卵巢低反应,6例卵巢肿瘤因素,前者共进行78个取卵周期,取卵周期获卵率55．1％,获卵周期受精率58．1％,取卵周期胚胎移植率21,8％,临床妊娠5例,3例已分娩,2例流产,移植周期临床妊娠率29．4％,流产率11．7％。而后者,6例共进行7个取卵周期,6个周期获得卵子,取卵周期获卵率85．7％,受精率100％,取卵周期胚胎移植率57．1％,2例妊娠已分娩,移植周期临床妊娠率50％。结论自然周期方案IVF—ET对于卵巢低反应者是一种简单有效方法。对应用促排卵药物存在高风险者,同样可取得成功妊娠。     

Cumulative pregnancy rates after a maximum of nine cycles of modified natural cycle IVF and analysis of patient drop-out: a cohort study

BACKGROUND: In modified natural cycle IVF (MNV-IVF), treatment is aimed at using the one follicle that spontaneously develops to dominance, using a GnRH antagonist together with gonadotrophins in the late follicular phase only. METHODS: In this single-centre cohort study, nine cycles of MNV-IVF were offered to 268 patients. Cumulative pregnancy rates (CPRs) were calculated and drop-out was analysed. The present study is an extension of earlier studies in which three cycles of MNV-IVF were offered to the same patients. RESULTS: A total of 256 patients completed 1048 cycles (4.1 per patient). Embryo transfer rate was 36.5% per started cycle. Ongoing pregnancy rate was 7.9% per started cycle and 20.7% per embryo transfer. Including treatment-independent pregnancies, the observed CPR after up to nine cycles was 44.4% (95% confidence interval 38.3-50.5) per patient. Pregnancy rates per started cycle did not decline in higher cycle numbers (overall 9.9%). Drop-out rates were high (overall 47.8%). We found that cancellation of oocyte retrieval, fertilization failure and failure to reach embryo transfer are repeating phenomena in subsequent cycles and furthermore that these events predispose for drop-out. CONCLUSIONS: CPR after nine cycles of MNV-IVF in this study was 44.4%. Pregnancy rate per cycle did not decline in higher cycle numbers, possibly due to selective drop-out of poor prognosis patients. Due to the low-risk and patient-friendly nature of the MNC protocol, it seems a feasible treatment option for patients requiring IVF.     

A meta-analysis of outcomes of conventional IVF in women with polycystic ovary syndrome

This meta-analysis was conducted to compare outcomes of conventional IVF in women presenting with polycystic ovary syndrome (PCOS) and non-PCOS patients. Studies in which PCOS patients undergoing IVF were compared with a matched--no male factor--control group were considered for this review. A definition consistent with the Rotterdam consensus criteria of PCOS was required, and all patients within a given study had to be treated with the same ovarian stimulation protocol. Information regarding patient characteristics and pregnancy outcome was also required. Nine out of 290 identified studies reporting data on 458 PCOS patients (793 cycles) and 694 matched controls (1116 cycles) fulfilled these inclusion criteria. PCOS patients demonstrated a significantly reduced chance of oocyte retrieval per started cycle, odds ratio (OR) = 0.5 [95% confidence interval (CI) = 0.2-1.0]. However, no difference was observed in chance of embryo transfer per oocyte retrieval between the groups (OR = 0.7, 95% CI = 0.4-1.3). Significantly more oocytes per retrieval were obtained in PCOS patients compared with controls [random effects estimate 3.4 [95% (CI) = 1.7-5.1)]. The number of oocytes fertilized did not differ significantly between PCOS patients and controls, weighted mean difference (WMD) 0.1 oocytes (95% CI = 21.4-1.6). No significant difference was observed in the clinical pregnancy rates per started cycle, OR = 1.0 (95% CI = 0.8-1.3). The incidence of ovarian hyperstimulation syndrome (OHSS) after oocyte retrieval was rarely reported. This meta-analysis demonstrates an increased cancellation rate, but more oocytes retrieved per retrieval and a lower fertilization rate in PCOS undergoing IVF. Overall, PCOS and control patients achieved similar pregnancy and live birth rates per cycle.     

Shortened exposure of oocytes to spermatozoa improves in-vitro fertilization outcome: a prospective, randomized, controlled study.

A prospective, randomized study of 158 patients undergoing in-vitro fertilization (IVF) and embryo transfer was conducted to evaluate whether a shortened exposure of oocytes to spermatozoa enhances oocyte development, and subsequently influences the IVF outcome. A comparison was made between conventional treatment time and shorter exposure of retrieved oocytes to spermatozoa. Fertilization and cleavage rates, embryo quality, implantation and pregnancy rates in the study group (short exposure) versus controls (standard IVF procedure) were evaluated. Fertilization (56 versus 61%) and cleavage rates (96 versus 92%) were similar in the two groups respectively. However, embryo quality was significantly higher in the study group (P < 0.05). Moreover, the pregnancy and implantation rates were significantly increased (42.4 versus 26% per embryo transfer, and 16 versus 10% respectively; P < 0.05). Our results demonstrated that shorter exposure of oocytes to spermatozoa is superior to the standard time in IVF and may have a favourable effect on implantation rates by improving embryo quality.